Machines, such as, for example, track-type tractors and other off-highway vehicles including construction, agriculture, and mining machines, are used to perform many tasks. To effectively perform these tasks, such machines require a power source that provides significant power to a drive system. The power source may be an engine such as, for example, a turbine engine, diesel engine, gasoline engine, or natural gas engine operated to generate a torque output at a range of speeds. This torque is typically provided to one or more traction devices via a transmission operably connected to the engine via the drive system.
To start such machines, a starter motor with the capability of generating a large amount of torque at low speeds is needed. Often the amount of electrical power required to operate a starter motor for a relatively short period of time can significantly drain the available power in a portable energy storage device such as a battery. In order to maintain sufficient power in the battery for multiple starts of the power source, an electrical generator such as an alternator is often provided to generate the electrical power needed to recharge the battery. If an induction motor is used as both a starter motor and as an alternator to generate electrical power, the induction motor must be able to operate at lower speeds and higher torque when starting the machine, and at higher speeds and lower torque while still generating sufficient power in its capacity as an alternator or generator.
An exemplary induction motor used as both a starter and an alternator is described in U.S. Pat. No. 5,977,679 (the '679 patent) issued to Miller et al. on Nov. 2, 1999. The '679 patent describes an induction motor including a stator having a cylindrical core with a plurality of inner and outer slots and a plurality of toroidal coils wound about the core and laid in the inner and outer slots. The design of the induction motor in the '679 patent is said to enable arbitrary combination of the number of poles and phases of the motor, thus allowing for smooth torque operation in the alternator mode.
Although the induction motor disclosed in the '679 patent may provide some advantages in allowing an induction motor to be used in both a starter mode and as an alternator, the motor still experiences a variety of drawbacks. For example, in order for the induction motor in the '679 patent to transition from engine cranking to alternator mode, the number of phases must be changed to accommodate a change in a number of poles. This required change in the number of phases also results in a significant increase in the electronic complexity of an inverter that is connected to the coils of the motor to allow multiphase operation.
The disclosed systems and methods are directed to overcoming one or more of the problems set forth above.